1. Field of the Invention
This invention has relation to the use of surge suppressors in the form of varistors to prevent random and switching transients in incoming power transmission lines from reaching electrical equipment connected to those lines, and the use of normally activated neon glow tubes or other voltage drop indicators to constantly simultaneously indicate that these surge suppressor circuits are in operative condition and to indicate that there is no short circuit in such transmission lines.
2. Description of the Prior Art
In alternating current power systems, it is known to connect a varistor between an incoming power line and the ground, and it is known to provide a fuse in series with this varistor. Further, it is known to connect a pilot light between a power line and neutral or ground to indicate the presence or absence of electrical energy in that line. Before the present invention, however, there was no way to indicate in a single unit both that the surge suppressor was in condition to operate properly to protect against overload surges and that there was no short circuit in the power lines.
One obvious advantage of using a surge suppressor and nonshort circuit monitor unit is to protect the electrical equipment connected to the incoming transmission lines from surges which can be damaging to that equipment. A less obvious but very important advantage is to prevent such surges from adversely affecting the readings on the electric watt meter. Transient overload surges add nothing to the performance of line electrical equipment on the surging lines, but do cause the watt meter to register a higher wattage than is actually used by the equipment.
Most electrical fires start because of short circuits. A major advantage of a combined nonshort circuit monitor and surge suppressor unit is that it gives an instantaneous indication of a condition where the absence of a short circuit can no longer be assumed. This allows instant remedial action to be taken.
A further advantage is that the visual indicator indicates simultaneously both the fact that the surge suppressor function is in place and operative and the fact that the incoming power lines are not shorted to ground or neutral.
In the parent application, the following were cited by the Examiner as prior art.
U.S. Pat. No. 4,191,985 to Phillips, Jr. in March 1980;
U.S. Pat. No. 3,693,053 to Anderson in September 1972;
U.S. Pat. No. 4,023,071 to Russell in May 1977;
U.S. Pat. No. 4,089,032 to Orfano in May 1978; and
U.S. Pat. No. 3,894,274 to Rosenberry, Jr. in July 1975.